Renal Nerve Denervation (RDN) has been performed via various techniques in order to block efferent and afferent sympathetic nerve activity between the central nervous system and the kidneys and nerves that are involved with vascular control in order to treat hypertension (HTN). One technique utilizes radiofrequency (RF) energy delivered to the nerves that surround the renal arteries to cause necrosis of the nerves and hence block sympathetic signaling. The RF energy can be delivered at specific sites along a perimeter of the renal artery at a location between the renal artery ostium at the aorta and sites located near or at the junction of the renal artery with the kidneys. Various catheters with RF electrodes located along the outside of a balloon or located otherwise in contact with the arterial wall have been used to effect such RF treatment of the renal artery. Other energy means have also been utilized to affect a blockage of the sympathetic signaling including the use of ultrasound (US) and delivery of neurotoxic chemicals including alcohol directly to the wall or within the wall of the renal artery.
The problem with the current devices is that they do not deliver the energy or chemical in a uniformly distributed manner to all regions of the renal arterial wall. Some sympathetic nerves that are located near a vein or other heat sink can be shielded or otherwise protected from the thermal aspects of RF or US energy that normally would result in nerve necrosis and can therefore allow one or more of the sympathetic nerves to remain viable. Nerves located further from the sites of chemical injection will be less susceptible to necrosis and subsequent sympathetic signal blockage. Excess use of either RF, US energy or use of chemical toxins can cause the renal artery to become damaged and could result in renal artery stenosis or renal artery aneurysm, either of which can be detrimental to the patient.
What is needed is a device and method that applies a uniform pressure or uniform severing to the sympathetic renal nerves along the perimeter of the renal artery wall and throughout its wall thickness such that the sympathetic renal nerves are completely blocked around the entire perimeter and blocked to a distance from the renal artery lumen that includes all of the sympathetic renal artery nerves.